Swapping The Sensor In A DSLR

To take a color image, modern digicams have something called a Bayer pattern – small red green and blue filters, one color for each pixel – that drastically reduce the resolution if all you’re doing is taking black and white pictures. [Lasse] is an astrophotographer, and doesn’t exactly need color pictures, so he decided to swap the color sensor in his camera with a monochrome CCD.

Most DSLRs have CCD sensors on strange surface mount packages or put everything on flex PCBs. [Lasse]’s Olympus E-500, though, features an 8 Megapixel CCD on a ceramic DIP that is actually fairly easy to remove given the right tools and just a little bit of mechanical encouragement.

After putting in a new monochrome CCD, [Lasse] had a much more sensitive sensor in his camera, and processing the RAW files off the camera gives him a great improvement for his astrophotography.

CCDs unlike CMOS are purely analogue devices and rely a lot on external circuitry for processing, biasing, and the ever critical analogue to digital conversion. The SBIG STF-8300 has a 16bit ADC, the E500 has a 12bit for starters, and that doesn’t even take into account the way the CCDs are handled (one camera is attempting to read out as carefully as possible, the other as quickly as possible).

For comparison I upgrade my D200 to a D800 and then for astronomy I ended up buying a QHY8 which has the same sensor as the D200, yet each time I got a large step change improvement in performance.

What was a bit strange to me here is this: isn’t it easier to fit a CCD camera to lens (supposedly the telescope itself might be enough of a lens) than to fit a CCD sensor to a camera and then still figure out how to fit it to the telescope anyway?

I have to plea ignorance of the costs of all components involved though but I thought I saw a CCD camera in the form factor of a telescope eye piece for something like $300 (admittedly, have no idea if it was any good) – about the cost of an entry level DSLR. So, what exactly is the motivation: saving costs, improving performance in some way or “just because I can” (also a valid reason)?

What you saw for 300$ is not much more than a USB webcam with a heatsink on it. About the only thing they have going for them is you should be able to just drop it in a scope and go. On the downside, it has sub-megapixel resolution, and each individual pixel will be smaller than that of the the APS-C sensor used in most DSLRs – increasing both noise and exposure times. Back in early 2000s these used to be worthwhile, but nowadays they’re more novelties ala. USB microscopes for kids.

it’s not painless to use a DSLR, though: at minimum, a method to mount the camera on the scope is required, and preferably the removal of the IR filter too. For bonus points, rig it for peltier cooling like this guy did http://ghonis2.ho8.com//rebelmod450d16c.html and reduce noise further. Best bet is to get a few generations old model, due to price, easier to modify, and larger pixels.

In short: the DSLR is higher resolution, requires shorter exposures, and will have less noisy images, in exchange for more money invested. However, the payoff is extreme: check the sample images in the link above. Of course, the 5000$ worth of gear has something to do with that…

Telescopes have a standard method of connecting to cameras via a T-thread. You can buy T-thread adapters for any camera mount. It’s no more difficult to mount a DSLR on a telescope then to screw a CCD onto the standard thread.

The motivation for DSLRs on the telescope is that you have a dual purpose device, and thus it’s quite the bit cheaper. Dedicated astro cameras require a computer, a lot of ancillary equipment, and can’t be used for anything other than astronomy.

Canon even make a version of the 60D called the 60Da for the very purpose of mounting to a telescope, and a company called Astronomik has created clip in IR blocking filters allowing cameras modified for increased IR sensitivity (good for taking photos of nebula) to be used normally.

Most dlsrs don’t have CCD sensors, some do, canons for instance use CMOS sensors. His olympus is using a ccd.

He does need pictures, he’s just not interested in RGB colour, he’s interested in increased resolution, he can also exploit the Infra Red sensitivity (if he doesn’t put the filter back in when he swaps the sensors out) and can now use specific filters that allow him to see deep space objects in more detail, his pictures will somewhat resemble the pictures from the hubble telescope (hubble doesn’t do real colour either).

His mod is pretty good, the results are clear to see, he says that he’s having trouble auto focusing, it’s possible that he’s missing filters from the original sensor (I hope he didn’t throw it) but the position of the sensor is very critical, coupled with the missing filters, it could be that he’ll need to shim something if that’s possible or replace the missing ir filter with a baader filter (if they make one for his camera).

it doesn’t swap out the sensor but the attention to detail to dismantle this thing is a tour de force in itself, just to remove the IR filter from the sensor assembly. I can’t remember if he replaces the IR filter or not but there will be a lot of useful information on why the cameras are modded and some comprehensive testing too.

I don’t think my pockets where ever deep enough dig this far into functioning item. However my pockets where never deep enough to purchase the product this hack emulates. I’m pretty sure anyone who suggests they never after proof reading a document found an error after posting or printing it might be bullshitting us. Sure simply pointing out an error is useful, but any editorializing beyond that serve no useful purpose, so I better stop doing myself. ;) An email link in the byline field would make it easier for any volunteer editors to advise the author of errors directly.

Sure, I’ve posted/published articles with errors, but nothing so bad as to make the reader believe that it wasn’t even read over ONCE. What’s worse is that, after many many friendly (and some not-so-friendly) reminders and hints, it still continues.

I do like your idea of a separate place/ an email address to post matters pertaining to editorial mishaps. This could go some way to keeping the discussion on topic.

Although perhaps taking things a bit too far, a secondary discussion thread on each article would allow those who take an active interest in this to continue to actively engage with each other over their observed errors and the proper remediation.

here’s a place that’ll actually remove the bayer filter from camera sensors in order to turn them in to b&w. http://maxmax.com/b&w_conversion.htm
The site is a nightmare to walk through but this guy is extremely knowledgeable. At work we purchased a rebel t1i from him a few years ago-it’s impressive what he’s able to do!

The problem:
– Some HaD readers really hate spelling errors.
– Other HaD readers really hate people who comment about spelling errors.

The solution:
– Get spelling moderators! The top five spelling complainers (measured in qty of spelling complaint comments) get moderator duty. You guys already spend time writing all those spelling complaints for free so what’s the difference? Appreciate that you’re given a platform to do what you love – correct spelling!
– Spelling moderators correct spelling only. Any change of substance merits punishment.
– Each post get an “alert the spelling moderators” button, for up and coming spelling fans to contact the spelling moderators elders.
– With the system up and running any spelling in comments is punished by forced eating of a raspberry pi.

When imaging the night sky a lot of the subjects emit light in narrowband. Ha and S-II in the infrared, Ozone in the Blues, etc. Depending on what you’re photographing 3/4 of the pixels on the sensor aren’t picking up any useful data.